Generally, an automatic document feeder and an image scanner are collectively defined as an automatic scanning apparatus to automatically scanning a plurality of paper sheets. Alternatively, an automatic document feeder and a printer are collectively defined as an automatic printing apparatus. The automatic document feeder can be used for feeding various types of documents with different sizes. For example, the automatic document feeder is widely employed to feed the A4-sized documents. As known, if the document is not confined at the middle region of the paper input tray, the document is readily aslant fed into the internal portion of the automatic document feeder. Under this circumstance, the scanning operation or the printing operation is usually incomplete. For solving this drawback, the paper input tray of the automatic document feeder is usually equipped with a document position-limiting mechanism for confining the document at the middle region of the paper input tray.
FIG. 1 is a schematic perspective view illustrating a document position-limiting mechanism installed on a paper input tray of an automatic document feeder according to the prior art. The document position-limiting mechanism 2 is applied to a paper input tray 1 of an automatic document feeder. The paper input tray 1 has a plurality of graduations 10, 11 and 12. These graduations 10, 11 and 12 are located at a first side of the document position-limiting mechanism 2. In addition, the graduations 10, 11 and 12 are shown on an outer surface 13 of the paper input tray 1, and arranged in a line. A first graduation 10 of these graduations corresponds to an A6-sized document. A second graduation 11 of these graduations corresponds to an A5-sized document. A third graduation 12 of these graduations corresponds to an A4-sized document.
The document position-limiting mechanism 2 comprises a first paper guide plate 20, a second paper guide plate 21 and a connecting wheel 22. The first paper guide plate 20 is disposed on the paper input tray 1. In addition, the first paper guide plate 20 comprises a first paper stopper 201 and a first rack 202. The first paper stopper 201 is exposed to the outer surface 13 of the paper input tray 1 for stopping a first edge of a document (not shown). The first rack 202 is disposed on an inner surface 14 of the paper input tray 1 and in contact with the connecting wheel 22.
Similarly, the second paper guide plate 21 is disposed on the paper input tray 1 and located at a side of the first paper guide plate 20. In addition, the second paper guide plate 21 comprises a second paper stopper 211 and a second rack 212. The second paper stopper 211 is exposed to the outer surface 13 of the paper input tray 1 for stopping a second edge of the document. The second rack 212 is disposed on the inner surface 14 of the paper input tray 1 and in contact with the connecting wheel 22. The connecting wheel 22 is arranged between the first paper guide plate 20 and the second paper guide plate 21, and contacted with and engaged with the first rack 202 of the first paper guide plate 20 and the second rack 212 of the second paper guide plate 21, respectively. Consequently, the first paper guide plate 20 and the second paper guide plate 21 are moved in opposite directions. That is, as the first paper guide plate 20 is moved in a first direction D1, the second paper guide plate 21 is moved in a second direction D2 opposite to the first direction D1 through the connecting wheel 22, and vice versa.
When the user wants to scan an A4-sized document, the document position-limiting mechanism 2 should be firstly adjusted to comply with the A4-sized document. The method of adjusting the document position-limiting mechanism 2 comprises the following steps. First of all, the first paper guide plate 20 is moved to the location corresponding to the third graduation 12 while the first paper guide plate 20 is aligned with the third graduation 12 by naked eyes. In response to movement of the first paper guide plate 20, the second paper guide plate 21 is moved to a corresponding location. Then, the A4-sized document is placed on the document position-limiting mechanism 2. Meanwhile, the first edge of the document is stopped by the first paper stopper 201 of the first paper guide plate 20, and the second edge of the document is stopped by the second paper stopper 211 of the second paper guide plate 21. In such way, the document will not be aslant fed into the internal portion of the automatic document feeder.
From the above discussions, the document position-limiting mechanism 2 has a plurality of graduations 10, 11 and 12. Before the document to be fed is placed on the paper input tray 1, the relative locations of the first paper guide plate 20 and the second paper guide plate 21 are adjusted according to the size of the document and the graduations 10, 11 and 12. Since the ways of recognizing the location of the graduation and aligning the first paper guide plate 20 with the graduation are very inconvenient for many users, another document position-limiting mechanism without the need of using the naked eyes to align the graduation has been disclosed.
FIG. 2 is a schematic perspective view illustrating another document position-limiting mechanism installed on a paper input tray of an automatic document feeder according to the prior art. FIG. 3 is a schematic bottom view illustrating the document position-limiting mechanism of FIG. 2. Please refer to FIGS. 2 and 3. The document position-limiting mechanism 4 is installed on a paper input tray 3 of an automatic document feeder. The paper input tray 3 has a plurality of graduations 30, 31 and 32. These graduations 30, 31 and 32 are located at a first side of the document position-limiting mechanism 4. In addition, the graduations 30, 31 and 32 are shown on an outer surface 33 of the paper input tray 3, and arranged in a line. A first graduation 30 of these graduations corresponds to an A6-sized document. A second graduation 31 of these graduations corresponds to an A5-sized document. A third graduation 32 of these graduations corresponds to an A4-sized document. As shown in FIG. 3, the paper input tray 3 further comprises a plurality of recesses 35, 36 and 37. These recesses 35, 36 and 37 are located at an inner surface 34 of the paper input tray 3. The first recess 35 of these recesses is aligned the first graduation 30. The second recess 36 of these recesses is aligned with the second graduation 31. The third recess 37 of these recesses is aligned with the third graduation 32.
The document position-limiting mechanism 4 comprises a first paper guide plate 40, a second paper guide plate 41 and a connecting wheel 42. The first paper guide plate 40 is disposed on the paper input tray 3. In addition, the first paper guide plate 40 comprises a first paper stopper 401 and a first rack 402. The first paper stopper 401 is exposed to the outer surface 33 of the paper input tray 3 for stopping a first edge of a document (not shown). The first rack 402 is disposed on the inner surface 34 of the paper input tray 3 and in contact with the connecting wheel 42.
Similarly, the second paper guide plate 41 is disposed on the paper input tray 3 and located at a side of the first paper guide plate 40. In addition, the second paper guide plate 41 comprises a second paper stopper 411, a second rack 412 and a protrusion 413. The second paper stopper 411 is exposed to the outer surface 33 of the paper input tray 3 for stopping a second edge of the document. The second rack 412 is disposed on the inner surface 34 of the paper input tray 3 and in contact with the connecting wheel 42. The protrusion 413 is located adjacent to the recesses 35, 36 and 37 of the paper input tray 3. As the second paper guide plate 41 is moved, the protrusion 413 is selectively inserted into one of these recesses 35, 36 and 37. The connecting wheel 42 is arranged between the first paper guide plate 40 and the second paper guide plate 41, and contacted with and engaged with the first rack 402 of the first paper guide plate 40 and the second rack 412 of the second paper guide plate 41, respectively. Consequently, the first paper guide plate 40 and the second paper guide plate 41 are moved in opposite directions.
When the user wants to scan an A4-sized document, the document position-limiting mechanism 4 should be firstly adjusted to comply with the A4-sized document. The method of adjusting the document position-limiting mechanism 4 comprises the following steps. First of all, the location of the third graduation 32 corresponding to the A4-sized document is realized by the naked eyes. Then, the second paper guide plate 41 is moved toward the location of the third graduation 32. As the second paper guide plate 41 is moved, the protrusion 413 of the second paper guide plate 41 is inserted into the third recess 37 corresponding to the third graduation 32. Whereas, in response to movement of the second paper guide plate 41, the first paper guide plate 40 is moved to a corresponding location. Then, the A4-sized document is placed on the document position-limiting mechanism 4. Meanwhile, the first edge of the document is stopped by the first paper stopper 401 of the first paper guide plate 40, and the second edge of the document is stopped by the second paper stopper 411 of the second paper guide plate 41. In such way, the document will not be aslant fed into the internal portion of the automatic document feeder.
In the conventional document position-limiting mechanism 4, the location of the second paper guide plate 41 can be fixed when the protrusion 413 of the second paper guide plate 41 is inserted into one of the recesses 35, 36 and 37. That is, the use of the document position-limiting mechanism 4 does not need to precisely align the graduations corresponding to various document sizes with the naked eyes. However, in comparison with the conventional document position-limiting mechanism 2 that can be applied to the documents of various sizes (including the unofficial document sizes), the conventional document position-limiting mechanism 4 is only used to confine the document of a special size (e.g. A4, A5 and A6). Therefore, there is need of providing a document position-limiting mechanism that is applicable to the documents of various sizes and can be easily operated without using the naked eyes to align the graduation.